1. Field of Invention
The present invention relates to a rotor which is formed using a printed wiring board and a small flat air-cored vibration motor having such a rotor and used for example in silent call means in a mobile telecommunication device and in MD devices.
2. Description of the Related Art
Conventionally, on one surface of a printed wiring board used in a rotor, an air-cored armature coil with a solder-connected terminal is disposed on a prescribed wiring pattern on the printed wiring board, and on the other surface a plurality of segment patterns constituting a commutator and a wiring pattern are disposed. Then by molding the printed wiring board and air-cored armature coil into a unitary body with a resin, in such manner that these segment patterns are exposed, a rotor for a flat coreless motor is formed. (For example, see JP, 10-248229, A.)
In the production method for such a rotor, first a printed wiring board is constituted such that on one side thereof a plurality of segment patterns constituting a commutator and a wiring pattern are disposed. On the side of the printed wiring board opposite the side on which a plurality of segment patterns constituting a commutator and a wiring pattern are disposed, an air-cored armature coil is solder-connected at its terminal to a prescribed wiring pattern. Thereafter, this printed wiring board is set in a mold and the air-cored armature coil and printed wiring board are molded with a resin to form a unitary body in such a manner that the segment patterns are exposed. In such manner a rotor is produced.
FIG. 4 shows a conventional example. However, as can be seen in FIG. 4, on a board surface 41b of a printed wiring board 41, segment patterns 42 forming a commutator with a thickness of roughly 40 μm and a wiring pattern are provided. When the printed wiring board 41 on which such parts are provided is set in a mold K for molding into a unitary body with a resin, the wiring pattern and segment patterns 42 come in contact with mold surface Ks, thus forming a gap S of roughly 40 μm between the mold surface Ks and the board surface 41b. 
When in such a state the mold is filled with a resin 47, and the resin 47 penetrates into this gap S forming a burr B. In some cases, the resin 47 that has penetrated into this gap S will even reach the space between adjoining segment patterns 42.
If a burr formed in the manner described above is present on a printed wiring board, when motor parts are assembled, a variety of problems may arise, such as the burr coming in contact with a case or magnet, causing interference defects, or else after assembly the burr breaking off and remaining as a foreign object within the motor.